Created attachment 129060[details]
Webkitgtk rendering errors in GtkLauncher
Another example. This one in the simplest possible browser (Gtklauncher). This shows the very common rendering error in the upper left.
(For another interesting UI rendering error, go to slashdot.org and scroll up and down rapidly. It renders UI circles and sometimes dashes).

I can confirm the exact same behavior with cross-compiled webkitgtk 1.6.x for Windows.
Native widgets are stacked up in the top left corner of the page, like in attachment:
https://bugs.webkit.org/attachment.cgi?id=129060
When page is scrolled widget disappears entirely.
When mis-rendered widget is visible sometimes you can
interact with it (for example check the checkbox).
This issue seems to be worked around somewhat when applying
-webkit-appearance: none;
style to the widgets, as it can be seen in third column of attachment:
https://bugs.webkit.org/attachment.cgi?id=129078
For the record:
Webkitgtk 1.4.2 cross compiled and run with the same version of libraries
behaves as intended. Widgets are in proper place, stay on scroll.
When using webkitgtk 1.7.x widgets are no longer stuck in the corner
and they stay in the proper place when scrolling as well.
Instead one can see black borders
around widgets like ones here:
http://kalev.fedorapeople.org/midori_about_widgets.png
Again applying --webkit-appearance: none; seems to help somewhat.

This issue is resolved if I switch from using my Windows X Window Server (x2go Windows client) to my VMWare vSphere console. The only failure mode common to myself and the other poster (tuxator) is that we are both using webkitgtk (1.6.x+) on a 'mingw' stack.
(I'm not sure I understand the implications of that. Perhaps it's a timing or other issue in the mingw support libraries, or perhaps it just exposes an already existing issue in webkitgtk. Certainly it's not anything in the X Window layer itself.)
Again, my vSphere console (running on Windows) does not exhibit the issue. Don't know why. The only difference is that mingw is not in the stack.
I don't have any way currently to test this problem on a physical console. Maybe tonight.

Confirming this behavior under a somewhat different set of circumstances than those previously listed.
I'm running two heads on a nvidia card with the proprietary driver using Xinerama, and all of my WebKitGTK browsers are exhibiting this. The interesting thing is that, when I run only one head, or on both heads using TwinView (neither being a particularly-appealing workaround), the behavior is no longer exhibited at all. This tells me that I'm getting this behavior as a result of a lack of xrandr extensions on my display, a state common to all setups I've seen this bug with. Given the odd assortment of environments associated with most of the comments in this report, like X over ssh and a Windows cross-compile, my (admittedly disclaimer-warranting) thinking is that a lack of information on the display is causing something in WebKit's GTK widgeting faculty to wig out (only GTK widgets on the page seem to be affected).
I'll be testing this on an assortment of other setups, but, so far, I've only been able to replicate in environments lacking xrandr extensions. Dual-head on an Intel IGP using xrandr seems to work fine.
For posterity's sake:
Midori 0.4.4
WebKitGTK+ 1.6.3 (1.6.3)
GTK+ 2.24.10 (2.24.10)
Glib 2.30.2 (2.30.2)
libsoup 2.36.1
cairo 1.10.2 (1.10.2)
libnotify 0.7.4
single instance libunique 1.1.6
Platform X11; Linux i686
Identification Mozilla/5.0 (Macintosh; U; Intel Mac OS X; en-us) AppleWebKit/535+ (KHTML, like Gecko) Version/5.0 Safari/535.4+ Midori/0.4
Video Formats H264 [x] Ogg Theora [x] WebM [x]

Hi,
I am seeing the same black borders issue with WebKiTGtk+-1.6.3. The WebKiTGtk+-1.2.x is fine in this respect.
I am compiling Webkit for an embedded system with Gtk-Directfb.
Did you have any success in figuring out the issue?
Regards
~Sameer

Comment on attachment 232259[details]
Black Boxes Around Inputs
I am having this black box issue surrounding inputs as well. Running Debian Jessie with libwebkitgtk-1.0-1 version 2.4.2-1 and midori version 0.5.8-1~trusty~ppa1.